1. Field of the Invention
The invention relates to a gas barrier substrate, and more particularly to, a gas barrier substrate with favorable gas barrier capability.
2. Description of Related Art
A base material of a display device determines whether the display device posses a flexibility. When a substrate of the display device is a rigid substrate, such as a glass substrate, the display device does not posses the flexibility. Contrarily, when the substrate of the display device is a flexible substrate, such as a plastic substrate, the display device is then possessed with a favorable flexibility.
Advantages of the flexible substrate, in comparative to the general rigid substrate, are cheap, transparent, easy processing, compliance with safety, suitable for all display medias, and suitable for a Roll-to-Roll process, but disadvantages thereof are high temperature intolerance, poor water and oxygen resistance, poor chemical resistance, and large thermal expansion coefficient. A penetration rate of the typical flexible substrate is 100 to 10−1 g/m2/day (25° C.). Because the typical flexible substrate cannot block the penetration of water vapor and oxygen completely, the aging of elements within the substrate is accelerated, causing the life-span of the produced elements to cut short, and is thereby unable to meet the business demands. Therefore, in order to block water and oxygen, a special material for densification is coated between the flexible substrate and an inorganic conductive layer to prevent the penetration and the diffusion of water and oxygen. The selection of this densification barrier material requires it to be capable of defect freely and evenly forming a film layer during a coating process, not producing pinholes, having high light transmittance, and avoiding absorption of visible light; and the densification barrier material achieves the gas barrier requirements of the flexible substrate with an arrangement of single layer or multilayer stacking.
Currently, a soft gas barrier film layer formed on the flexible substrate includes an organic film layer and an inorganic film layer, the inorganic film layer is, for example, a metal oxide, a metal nitride, a metal oxynitride, and the likes, wherein the gas resistance of the inorganic film layer is better than that of the organic film layer, and the organic film layer may maintain the softness of the overall gas barrier film layer. However, if a thickness of the inorganic film layer is increased to enhance the characteristic of blocking water and oxygen, the excessively thick inorganic film layer would be easily prone to produce a crack during bending, and thus an avoidance of a gas barrier film layer failure caused by a stress concentration has become important.